Thin-film transistor, thin-film transistor sheet and their manufacturing method

ABSTRACT

Disclosed are a process of manufacturing a thin-film transistor sheet and a thin-film transistor sheet manufactured by the process, the process comprising the steps of providing a gate busline on a substrate, providing, on the surface of the substrate busline side, an insulation layer capable of receiving a fluid electrode material, supplying the fluid electrode material to the insulation layer, the fluid electrode material being allowed to permeate the insulation layer, forming a gate electrode from the permeated fluid electrode material to be in contact with the gate busline, forming a gate insulating layer on the gate electrode, and forming a semiconductor layer on the gate insulating layer.

FIELD OF THE INVENTION

[0001] The present invention relates to a thin-film transistor, athin-film transistor sheet, and their manufacturing method.

BACKGROUND OF THE INVENTION

[0002] In recent years, with the spread of information terminals, thereare increasing demands for a flat panel display that serves as a displayfor a computer. Further, with development of the information technology,there has been increased a chance for information offered in a form of asheet of paper medium in the past to be offered in an electronic form.An electronic paper or a digital paper is demanded increasingly as adisplay medium for a mobile that is thin, lightweight and handy.

[0003] In the case of a display device of a flat sheet type, a displaymedium is generally formed using an element that employs a liquidcrystal, organic EL or electrophoresis method. In the display medium ofthis kind, a technology for using an active driving element comprised ofa thin-film transistor (TFT), serving as an image driving element, isthe main current for ensuring uniform image brightness and an imagerewriting speed.

[0004] A TFT is ordinarily manufactured by a process comprising forming,on a glass substrate, a semiconductor layer of a-Si (amorphous silicone)or p-Si (poly-silicone) and metal films of source, drain and gateelectrodes, in the order. In the manufacture of a flat panel displayemploying such a TFT, a photolithography step with high precision isrequired in addition to a thin layer forming step requiring a vacuumline carrying out a CVD method or a sputtering method or a hightemperature treatment step, which results in great increase ofmanufacturing cost or running cost. Recent demand for a large-sizeddisplay panel further increases those costs described above.

[0005] In order to overcome the above-described defects, an organicthin-film transistor employing an organic semiconducting material hasbeen extensively studied (see, for example, Japanese Patent O.P.I.Publication No. 10-190001 1 and “Advanced Material”, 2002, No. 2, p. 99(review)). Since the organic thin-film transistor can be manufactured atlow temperature employing a lightweight substrate difficult to bebroken, a flexible display employing a resin film as a substrate can berealized (see, for example, SID '02 Digest P. 57). Further, employing anorganic semiconducting material allowing a wet process such as aprinting method or a coating method, a display manufacturing process,which provides excellent productivity and reduced cost, is expected tobe realized.

[0006] A conventional manufacturing process of a TFT or a TFT sheetcomprises forming a film of a metal such as chromium, nickel or aluminumaccording to a sputtering method, and processing the film according tophotolithography including etching to form a gate busline or a gateelectrode. However, this process has problems in that gate leakage islikely to occur which is caused by minute unevenness of the electrodesurface, unevenness (herein also referred to as hillocks) of a layeradjacent to the electrode, which deteriorates smoothness of theelectrode surface, or edge portions of the electrode.

[0007] Further, there is problem that a TFT or a TFT sheet employing aresin sheet substrate, in which unevenness of the sheet surfacedeteriorates smoothness of the electrode surface, is likely to leak fromthe gate busline or the gate electrode, as compared with a conventionalTFT or TFT sheet employing a glass plate having a smooth surface.

SUMMARY OF THE INVENTION

[0008] The present invention has been made in view of the above. Anobject of the invention is to minimize gate leakage caused by thehillocks or edge portions of the electrode in a TFT panel or in a TFTsheet, and particularly to minimize gate leakage when a resin sheet isused as a substrate of the TFT panel or the TFT sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is one embodiment showing a structure of the TFT sheet ofthe invention.

[0010]FIG. 2 is a schematic equivalent circuit diagram of one example ofthe TFT sheet of the invention.

[0011]FIG. 3 is an illustration showing one pixel comprising a gateelectrode formed by fluid electrode material having permeated aninsulation layer capable of receiving the fluid electrode material, theinsulation layer being provided on a gate busline.

[0012]FIG. 4 is an illustration showing the position relationshipbetween a gate busline and a gate electrode.

[0013]FIG. 5 shows one embodiment of the structure of the thin-filmtransistor in the invention.

[0014]FIG. 6 shows another embodiment of the structure of the thin-filmtransistor in the invention.

[0015]FIG. 7 shows one embodiment of the structure of the thin-filmtransistor sheet in the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0016] The above object of the invention can be attained by thefollowing constitutions.

[0017] What is claimed is:

[0018] 1. A thin-film transistor comprising a substrate and providedthereon, an insulation layer capable of receiving a fluid electrodematerial, a gate electrode, a gate insulating layer, a semiconductorlayer, a source electrode and a drain electrode, the source electrodeand the drain electrode connecting each other through the semiconductorlayer, wherein the gate electrode is formed from the fluid electrodematerial which has been allowed to permeate the insulation layer.

[0019] 2. The thin-film transistor of item 1 above, wherein thesubstrate is comprised of a resin.

[0020] 3. The thin-film transistor of item 1 above, wherein the fluidelectrode material is a solution of an electrically conductive polymeror a dispersion liquid of an electrically conductive polymer.

[0021] 4. The thin-film transistor of item 1 above, wherein thesemiconductor layer is comprised of an organic semiconductor material.

[0022] 5. A process of manufacturing a thin-film transistor sheet, theprocess comprising the steps of providing a gate busline on a substrate,providing, on the surface of the substrate on the gate busline side, aninsulation layer capable of receiving a fluid electrode material,supplying the fluid electrode material to the insulation layer, thefluid electrode material being allowed to permeate the insulation layer,forming a gate electrode from the permeated fluid electrode material tobe in contact with the gate busline, forming a gate insulating layer onthe gate electrode, and forming a semiconductor layer on the gateinsulating layer.

[0023] 6. The process of item 5 above, wherein the substrate iscomprised of a resin.

[0024] 7. The process of item 5 above, wherein the fluid electrodematerial is a solution of an electrically conductive polymer or adispersion of an electrically conductive polymer.

[0025] 8. The process of item 5 above, wherein the semiconductor layeris comprised of an organic semiconductor material.

[0026] 9. The process of item 5 above, between the step of theinsulation layer providing step and the fluid electrode materialsupplying step, further comprising the step of supplying a resinsolution so that the resin is allowed to permeate portions other thanportions of the insulation layer where the gate electrode is to beformed.

[0027] 10. The process of item 5 above, wherein the semiconductor layeris formed as a continuous layer wherein the semiconductor layer isformed as a continuous layer over the entire surface on which thesemiconductor layer is to be formed.

[0028] 11. A thin-film transistor sheet manufactured according to theprocess of item 5 above.

[0029] 1-1 A thin-film transistor comprising a substrate and providedthereon, a gate electrode, a gate insulating layer, and a semiconductorlayer in that order, a source electrode and a drain electrode connectingeach other through the semiconductor layer, wherein the gate electrodeis formed from a fluid electrode material which has been allowed topermeate an insulation layer capable of receiving the fluid electrodematerial.

[0030] 1-2 The thin-film transistor of item 1-1 above, wherein thesubstrate is comprised of a resin.

[0031] 1-3 The thin-film transistor of item 1-1 or 1-2 above, whereinthe fluid electrode material is a solution of an electrically conductivepolymer or a dispersion liquid of an electrically conductive polymer.

[0032] 1-4 The thin-film transistor of any one of items 1-1 through 1-3above, wherein the semiconductor layer is comprised of an organicsemiconductor material.

[0033] 1-5 A process of manufacturing a thin-film transistor sheet, theprocess comprising the steps of providing a gate busline on a substrate,providing an insulation layer on the substrate surface on the gatebusline side, the insulation layer being capable of receiving a fluidelectrode material; and forming a gate electrode by supplying the fluidelectrode material to the insulation layer where the fluid electrodematerial is allowed to permeate the insulation layer.

[0034] 1-6 The process of item 1-5 above, wherein the substrate iscomprised of a resin.

[0035] 1-7 The process of item 1-5 or 1-6 above, wherein the fluidelectrode material is a solution of an electrically conductive polymeror a dispersion of an electrically conductive polymer.

[0036] 1-8 The process of any one of items 1-5 through 1-7 above,wherein the semiconductor layer is comprised of an organic semiconductormaterial.

[0037] 1-9 A thin-film transistor sheet manufactured according to theprocess of any one of items 1-5 through 1-8 above.

[0038] The present inventor has made a study on a method of forming agate electrode with a smooth surface such that the smoothness of thegate electrode surface is not deteriorated by unevenness of thesubstrate surface, etc., and has completed the invention.

[0039] The present invention will be detailed below.

[0040] The thin-film transistor of the invention is characterized inthat the gate electrode is formed from a fluid electrode material whichhas been allowed to permeate an insulation layer (hereinafter alsoreferred to simply as insulation layer) capable of receiving the fluidelectrode material.

[0041] In the invention, the fluid electrode material is a solution ofan electrically conductive material or a dispersion liquid of anelectrically conductive material. As the electrically conductivematerial, an electrically conductive polymer or metal particles aresuitably used, and an electrically conductive polymer is preferablyused.

[0042] As a solvent or dispersion medium for the fluid electrodematerial solution or dispersion in the invention, water or any solventcan be used, however, the solvent or dispersion medium preferablycontains water in an amount of not less than 30 by weight, in view ofits affinity to the insulation layer described later. The solvent usedis preferably a water soluble organic solvent.

[0043] Examples of the water soluble organic solvent usable in theinvention include alcohols (for example, methanol, ethanol, isopropanol,butanol, isobutanol, secondary butanol, tertiary butanol, pentanol,hexanol, cyclohexanol, and benzyl alcohol); polyhydric alcohols (forexample, ethylene glycol, diethylene glycol, triethylene glycol,polyethylene glycol, propylene glycol, dipropylene glycol, polypropyleneglycol, butylene glycol, hexane diol, pentane diol, glycerin, pentanetriol, and thioglycol); polyhydric alcohol ethers (for example, ethyleneglycol monomethyl ether, ethylene glycol monoethyl ether, ethyleneglycol monobutyl ether, propylene glycol monomethyl ether, propyleneglycol monobutyl ether, ethylene glycol monomethyl ether acetate,triethylene glycol monomethyl ether, triethylene glycol monoethyl ether,triethylene glycol monobutyl ether, ethylene glycol monophenyl ether,and propylene glycol monophenyl ether); amines (for example,ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine,N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine,diethylenediamine, triethylenetetramine, tetraethylenepentamine,polyethylene imine, pentamethyldiethylenetriamine, andtetramethylpropylenediamine); amides (for example, formamide.N,N-dimethylformamide, and N,N-dimethylacetamide); heterocycliccompounds (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone,cyclohexylpyrrolidone, 2-oxazolidone, and 1,3-dimethyl-2-imidazolidinone); sulfoxides (for example,dimethylsulfoxide); sulfones (for example, sulfolane); urea;acetonitrile and acetone. The water soluble organic solvents arepreferably polyhydric alcohols, and more preferably mixtures ofpolyhydric alcohols and plyhydric alcohol ethers.

[0044] These water soluble organic solvents may be used singly or as amixture of two or more thereof. The content of the water soluble organicsolvent is preferably from 5 to 70% by weight, and more preferably from10 to 30% by weight based on the total content of the solvent used.Various surfactants can be used. It is preferred that a surfactant isadded to an electrically conductive material solution or dispersion usedparticularly in an ink jet method so as to give a surface tension offrom 30×10⁻³ to 40×10⁻³ N/m. When an electrically conductive polymerdoped with an anion is used, a nonionic surfactant is especiallysuitably used. The electrically conductive material solution ordispersion used in the ink jet method has a viscosity of preferably from1 to 15 cp, the viscosity being obtained by adjusting the concentrationof the electrically conductive material of the solution or dispersion.

[0045] Further, known electrically conductive polymers whose electricalconductivity is improved by doping are preferably used. Examples thereofinclude electrically conductive polyaniline, electrically conductivepolypyrrole, electrically conductive polythiophene, and complex ofelectrically conductive polyethylenedioxythiophene and polystyrenesulfonic acid.

[0046] As the electrically conductive polymer, a semiconductivematerial, preferably a π-conjugate oligomer or polymer used in thesemiconductor layer described later, which has been subjected to dopingtreatment, is preferably used. Examples thereof include apoly(ethylenedioxythiophene)-polystyrene sulfonic acid complex(PEDOT/PSS complex, for example, Baytron P produced by Bayer Co., Ltd) Adopant used in the doping treatment is preferably an anionic dopant(p-type dopant) in view of stability. The conductivity of theelectrically conductive polymer is preferably not less than 0.01 S/cm,and more preferably not less than 1 S/cm.

[0047] The doping herein means that an electron accepting molecule(acceptor) or an electron donating molecule (donor) is incorporated inthe oligomer or polymer described above as a dopant. Employed as thedopant used in the present invention may be either acceptor or donor.

[0048] Examples of the acceptor include halogens such as Cl₂, Br₂, I₂,ICl, ICl₃, IBr, and IF; Lewis acids such as PF₅, AsF₅, SbF₅, BF₃, BCl₃,BBr₃, and SO₃; protonic acids such as HF, HCl, HNO₃, H₂SO₄, HCIO₄,FSO₃H, ClSO₃H, and CF₃SO₃H; organic acids such as acetic acid, formicacid, and amino acid; transition metal compounds such as FeCl₃, FeOCl,TiCl₄, ZrCl₄, HfCl₄, NbF₅, NbF₅, NbCl₅, TaCl₅, MoCl₅, WF₅, WCl₅, UF₆,LnCl₃ (Ln=lanthanoid such as La, Ce, Nd, and Pr, and Y), and electrolyteanions such as Cl⁻, Br⁻, I⁻, ClO⁴⁻, PF⁶⁻, AsF⁵⁻, SbF⁶⁻, BF⁴⁻, and asulfonate anion.

[0049] Examples of the donor include alkali metals such as Li, Na, K,Rb, and Cs; alkaline earth metals such as Ca, Sr, and Ba; rare earthmetals such as Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb; anammonium ion; R₄P⁺, R₄AS⁺, and R₃S⁺; and acetylcholine.

[0050] Doping these dopants may be carried out employing anyconventional method, for example, a method in which the dopants areincorporated into an organic semiconductor layer having been formed or amethod in which the dopants are incorporated into an organicsemiconductor layer while the layer is formed. The former methodsinclude a gas phase doping in which gaseous dopants are employed, aliquid phase doping in which doping is carried out while the layer isbrought into contact with a dopant solution or a liquid dopant, and asolid phase doping in which diffusion doping is carried out while thelayer is brought into contact with a solid dopant so that the dopantdiffuse into the layer. In the liquid phase doping, it is possible toadjust the doping efficiency by means of electrolysis. In the lattermethod, a solution or a dispersion each containing an organicsemiconductor material and a dopant may be coated and subsequentlydried. For instance, when a vacuum deposition method is used, dopantsmay be incorporated in the layer by co-deposition of an organicsemiconductor material and a dopant. Further, when the layer is formedemploying a sputtering method, sputtering is carried out utilizing thetwo targets of an organic semiconductor material and a dopant, wherebythe dopant can be incorporated in the layer. Still further, as othermethods, it is possible to use any of chemical doping such aselectrochemical doping or photoinitiation doping, or physical dopingsuch as an ion injection method as shown in, for example, a publication“Kogyo Zairyo”, Volume 34, No. 4, page 55 (1986).

[0051] As the dispersion liquid of metal particles, known electricallyconductive pastes may be used, but a dispersion liquid, in which metalparticles with a particle size of from 1 to 50 nm, and preferably from 1to 10 nm, is preferably used.

[0052] Materials for the metal particles include platinum, gold, silver,nickel, chromium, copper, iron, tin, antimony, lead, tantalum, indium,palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium,molybdenum, tungsten, and zinc.

[0053] The dispersion liquid of metal particles is preferably a metalparticle dispersion liquid in which metal particles of these metals aredispersed in a dispersion medium such as water or an organic solvent inthe presence of an organic dispersion stabilizer.

[0054] Methods for preparing such a metal particle dispersion liquidinclude a physical preparation method such as a gas vaporization method,a sputtering method, or a metallic vapor preparation method and achemical preparation method such as a colloid method or aco-precipitation method in which metal ions are reduced in a liquidphase to produce metal particles. The metal particles dispersion arepreferably ones prepared according to a colloid method disclosed inJapanese Patent O.P.I. Publication Nos. 11-76800, 11-80647, 11-319538,and 2000-239853, or ones prepared according to a gas vaporization methoddisclosed in Japanese Patent O.P.I. Publication Nos. 2001-254185,2001-53028, 2001-35814, 2001-35255, 2001-124157 and 2000-123634. Anelectrode pattern is formed from these metal particle dispersions dried,and optionally subjected to heat treatment at from 100 to 300° C., andpreferably from 150 to 200° C., whereby the metal particles areheat-fused to form an electrode or a circuit in an intended form.

[0055] In order to form a gate electrode comprised of the fluidelectrode material which has been allowed to permeate the insulationlayer capable of receiving the fluid electrode material, the fluidelectrode material may be ejected in the electrode pattern onto theinsulation layer according to an ink jet process, or may be printed inthe electrode pattern onto the insulation layer according to a printingmethod such as letterpress printing, intaglio printing, planographicprinting or screen printing. As an ink jet head of an ink jet printerused in the ink jet method, a conventional ink jet head such as a piezotype of a thermal type can be suitably used. The ink jet printer may beof on-demand type or continuous type.

[0056] Next, the insulation layer capable of receiving a fluid electrodematerial will be explained.

[0057] The insulation layer is a layer which the electrically conductivematerial permeates. The insulation layer can be divided into two typesof layers, that is, a swellable insulation layer and a void-containinginsulation layer.

[0058] The swellable insulation layer contains gelatin, a water solublepolymer other than gelatin, latexes, and polyurethanes, which may beused singly or in combination. The swellable insulation layer preferablycontains gelatin or a water soluble polymer other than gelatin, in viewof its high ink absorption and drying property.

[0059] As gelatin, any gelatin made from animal collagen can be used,but gelatin made from pig skin, cow skin or cow bone collagen ispreferable. The kind of gelatin is not specifically limited, butlime-processed gelatin, acid processed gelatin or gelatin derivatives(for example, gelatin derivatives disclosed in Japanese PatentPublication Nos. 38-4854, 39-5514, 40-12237, and 42-26345, U.S. Pat.Nos. 2,525,753, 2,594,293, 2,614,928, 2,763,639, 3,118,766, 3,132,945,3,186,846 and 3,312,553 and British Patent Nos. 861,414 and 103,189) canbe used singly or in combination. The acid processed gelatin isadvantageously used in view of water resistance.

[0060] Examples of the water soluble polymer other than gelatinpreferably used in the swellable insulation layer include polyvinylalcohol, polyvinyl pyrrolidone, polyvinyl pyridinium halide, modifiedpolyvinyl alcohol such as polyvinyl formal or their derivatives (seeJapanese Patent O.P.I. Publication Nos. 60-145879, 60-220750, 61-143177,61-235182, 61-235183, 61-237681 and 61-261089), an acrylgroup-containing polymer (disclosed in Japanese Patent O.P.I.Publication Nos. 168651/1985 and 9988/1987) such as polyacrylamide,polydimethylacrylamide, polydimethylaminoacrylate, poly(sodiumacrylate),a salt of methacrylic acid-acrylic acid copolymer,poly(sodiummethacrylate), or acrylic acid-vinyl alcohol copolymer, anatural polymer or its derivatives (disclosed in Japanese Patent O.P.I.Publication Nos. 59-174382, 60-262685, 61-143177, 61-181679, 61-193879and 61-287782) such as starch, oxidation starch, carboxylated starch,dialdehyde starch, cationated starch, dextrin, sodium alginate, gumarabic, casein, pullulan, dextrane, methylcellulose, ethylcellulose,carboxymethylcellulose or hydroxypropylcellulose, and a syntheticpolymer (disclosed in Japanese Patent O.P.I. Publication Nos. 61-32787,61-237680 and 61-277483) such as polyethylene glycol, polypropyleneglycol, polyvinyl ether, polyglycerin, maleic acid-alkylvinylethercopolymer, maleic acid-N-vinylpyrrole copolymer, styrene-maleicanhydride copolymer or polyethylene imine). Of these, the preferable arepolyvinyl pyrrolidones, polyvinyl alcohols or polyalkylene oxides.

[0061] The void-containing insulation layer is preferably a coated layerof a composition containing fine particles and optionally a watersoluble binder.

[0062] Listed as fine particles usable for the void-containing inkreceptive layer are inorganic particles or organic particles. Inorganicparticles are preferred, since fine particles are easily obtained.Examples of the inorganic particles include white inorganic pigmentssuch as, for example, precipitated calcium carbonate, heavy calciumcarbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate,barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zincsulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceousearth, calcium silicate, magnesium silicate, synthetic non-crystallinesilica, colloidal silica, alumina, colloidal alumina, false boehmite,aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, and thelike. The particles may exist in the void-containing insulation layer inthe form of primary particles, or aggregated secondary particles.

[0063] The inorganic particles are preferably alumina, false boehmite,colloidal silica, or silica particles synthesized by a gas phase method,and more preferably silica particles synthesized by a gas phase method.The silica particles synthesized by a gas phase method may be thosesurface-treated with Al. The Al content of the silica particlessurface-treated with Al is from 0.05 to 5% by weight based on thesilica.

[0064] The particle size of the particles may be any, but is preferablynot more than 1 μm, more preferably not more than 0.2 μm, and mostpreferably not more than 0.1 μm. Herein, the lower limit of the particlesize is not specifically limited, but is preferably, more preferably notless than 0.003 μm, and more preferably not less than 0.005 μm, in viewof manufacture of the particles.

[0065] The average particle size of the particles described above isdetermined in such a manner that particles located at the cross-sectionor the surface of the porous layer are observed employing an electronmicroscope, the size of randomly selected 100 particles are determined,and the simple average (arithmetic average) is computed. The particlesize of the individual particle is expressed in terms of a diameter of acircle having the same area as the projected area of the particle.

[0066] The particles may exist in the porous layer in the form ofprimary particles, secondary particles or higher order particles. Theparticles used for the calculation of the average particle size arethose independently existing in the porous layer.

[0067] The particle content of the aqueous coating solution ispreferably from 5 to 40% by weight, and more preferably from 7 to 30% byweight.

[0068] The water soluble binder contained in the void-containinginsulation layer is not specifically limited, and may be any known watersoluble binder. Examples of the water soluble binder include gelatin,polyvinyl pyrrolidone, polyethylene oxide, polyacryl amide and polyvinylalcohol. Polyvinyl alcohol is especially preferred.

[0069] Polyvinyl alcohol interacts with the inorganic particles,exhibits strong retention property to the inorganic particles, and isrelatively low in humidity dependency of hygroscopic property. Thepolyvinyl alcohols preferably used in the invention include an ordinarypolyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, and amodified polyvinyl alcohol such as a cation-modified polyvinyl alcoholor an anion-modified polyvinyl alcohol.

[0070] The polyvinyl alcohol obtained by hydrolyzing polyvinyl acetatehas an average polymerization degree of preferably not less than 300,and more preferably 1000 to 5,000. The polyvinyl alcohol has asaponification degree of preferably 70 to 100%, and more preferably 80to 99.5%.

[0071] The cation-modified polyvinyl alcohol is a polyvinyl alcoholhaving a primary to tertiary amino group or a quaternary ammonium groupin its main or side chain, and is obtained by saponifying a copolymer ofvinyl acetate and an ethylenically unsaturated monomer having a cationicgroup.

[0072] Examples of the ethylenically unsaturated monomer having acationic group includetrimethyl-(2-acrylamide-2,2-dimethylethyl)ammonium chloride,trimethyl-(3-acrylamide-3,3-dimethylpropyl)ammonium chloride,N-vinylimidazole, N-vinyl-2-methylimidazole,N-(3-dimethylaminopropyl)methacrylamide, hydroxyethyltrimethylammoniumchloride, trimethyl-(3-methacrylamidopropyl)ammonium chloride, andN-(1,1-dimethyl-3-dimethylaminopropyl)acrylamide.

[0073] The content of the monomer having a cationic group in thecation-modified polyvinyl alcohol is preferably 0.1 to 10 mol %, morepreferably 0.2 to 5 mol %, based on the vinyl acetate content.

[0074] Examples of the anion-modified polyvinyl alcohol includepolyvinyl alcohol having an anionic group disclosed in Japanese PatentO.P.I. Publication No. 1-206088, a copolymer of vinyl alcohol and avinyl compound having a water-solubilizing group disclosed in JapanesePatent O.P.I. Publication Nos. 61-237681 and 63-307979, and a modifiedpolyvinyl alcohol having a water-solubilizing group disclosed inJapanese Patent O.P.I. Publication Nos. 7-285265.

[0075] Examples of the nonion-modified polyvinyl alcohol include apolyvinyl alcohol derivative prepared by the addition of polyethyleneoxide to a part of hydroxy groups of polyvinyl alcohol disclosed inJapanese Patent O.P.I. Publication No. 7-9758, and a block copolymer ofa vinyl compound having a hydrophobic group and vinyl alcohol disclosedin Japanese Patent O.P.I. Publication No. 8-25795.

[0076] Polyvinyl alcohols can be used as a mixture of two or morethereof, according to the polymerization degree and kinds ofmodification. When polyvinyl alcohol with a polymerization degree of notless than 2000, polyvinyl alcohol with a polymerization degree of notmore than 1000 is in advance added in an amount of 0.05 to 10% byweight, and preferably 0.1 to 5% by weight based on the inorganicparticle weight to an inorganic particle dispersion, and then thepolyvinyl alcohol with a polymerization degree of not more than 1000 isadded, which exhibits no marked viscosity increase.

[0077] The content ratio of the particles to the water soluble polymerin the void-containing insulation layer is preferably 2 to 20 by weight.This ratio in the void-containing insulation layer maintains a propervoid ratio and sufficient void volume, prevents an excessive watersoluble polymer binder from swelling and clogging the voids during inkjet printing, maintains a proper absorption speed of the electricallyconductive material, and prevents cracks from occurring in thevoid-containing insulation layer. The content ratio of the particles tothe water soluble polymer in the void-containing insulation layer ismore preferably 2.5 to 12, and still more preferably 3 to 10.

[0078] In the invention, the insulation layer is preferably thevoid-containing insulation layer. The void-containing insulation layerincreases permeation speed of the electrode material and improvesaccuracy of the electrode pattern. The electrical conductivity ofportions of the insulation layer which the electrode material havepermeated is high as compared with that of the swellable insulationlayer. Further, kinds of fine particles or the water soluble polymer canbe suitably selected according to properties of the electricallyconductive material, and the permeation speed of the electricallyconductive material can be easily adjusted.

[0079] The thickness of the insulation layer is preferably from 0.05 to50 μm, and more preferably from 0.5 to 20 μm.

[0080] The TFT of the invention is preferably a bottom gate type one inwhich comprises a substrate and provided thereon, a gate electrode, agate insulating layer, and channel made of a semiconductor layer in thatorder, a source electrode and a drain electrode combining with eachother through the channel. The TFT sheet is one in which many of the TFTare arranged on a sheet substrate so that the TFTs are connected througha gate busline and a source busline, as is shown in FIG. 1. In FIG. 1,numerical number 2 represents gate electrode, numerical number 4 asemiconductor layer, numerical number 5 a source electrode, numericalnumber 6 a drain electrode, numerical number 12 a gate busline, andnumerical number 13 a source busline.

[0081]FIG. 2 is a schematic equivalent circuit diagram of one example ofthe thin-film transistor sheet, in which many TFTs are arranged.

[0082] The thin-film transistor sheet 11 comprises many of thin-filmtransistor 14 arranged in a matrix form. Numerical number 12 is a gatebusline of the gate electrode of the thin-film transistor 14, andnumerical number 13 a source busline of the source electrode of thethin-film transistor 14. Output element 16 is connected to the drainelectrode of the thin-film transistor 14. The output element 16 is forexample, a liquid crystal or an electrophoresis element, and constitutespixels in a display. In FIG. 2, liquid crystal as output element 16 isshown in an equivalent circuit diagram comprised of a capacitor and aresistor. Numerical number 15 shows a storage capacitor, numericalnumber 17 a vertical drive circuit, and numerical number 18 a horizontaldrive circuit.

[0083]FIG. 3 is an illustration showing a structure of one pixel. Thestructure is obtained by forming insulation layer 8 capable of receivinga fluid electrode material on gate busline 12 which is provided on asubbing layer 7 on substrate 1, and forming gate electrode 2 comprisedof the fluid electrode material, which has been supplied to theinsulation layer and has been allowed to permeate the insulation layer,so that the gate electrode 2 connects the gate busline 12.

[0084] Arrangement of the gate electrode 2 may be any as long as itconnects the gate busline 12, as is shown in FIG. 4(a) or 4(b).

[0085]FIG. 5 shows one embodiment of the structure of the thin-filmtransistor in the invention. FIG. 6 shows another embodiment of thestructure of the thin-film transistor in the invention. In FIGS. 5 and6, numerical number 1 is a substrate, numerical number 2 is a gateelectrode, numerical number 3 a gate insulating layer, numerical number4 a semiconductor layer, numerical number 5 a drain electrode, andnumerical number 6 a source electrode, and numerical number 8 aninsulation layer capable of receiving a fluid electrode material.

[0086]FIG. 7 shows one embodiment of the structure of the thin-filmtransistor sheet in the invention. In FIG. 7, the semiconductor layer 4is coated as a continuous layer on the entire surface on which thesemiconductor layer is to be formed. Electrode 10 is formed in theinsulation layer at the additional capacitor 20 in the same way as thegate electrode 2. In FIG. 7, numerical number 5 is a drain electrode,numerical number 6 a source electrode, numerical number 9 an outputelectrode, numerical number 12 a gate busline, and numerical number 13 asource busline.

[0087] Thus, the method, comprising forming the insulation layer andthen forming the gate electrode comprised of a fluid electrode materialwhich has been supplied to the insulation layer and has been allowed topermeate the insulation layer, levels the insulation layer surface andprovides the gate electrode having a smooth surface on the semiconductorlayer side. The smooth surface of the gate electrode thus obtained canprevent gate leakage or breakdown caused by unevenness such as hillocks,and can also prevent gate leakage or breakdown caused by edge portionsof the gate busline or the gate electrode often integrated with the gatebusline.

[0088] In addition, lowering of thin-film transistor yield orfluctuation of thin-film transistor performance, which is attributed todeterioration of smoothness of an interface between the organicsemiconductor layer and the gate electrode caused by the hillocks oredge portions, can be minimized.

[0089] In view of layer properties such as layer surface smoothness,layer thickness stability and thin layer formation ability, sputteringlayers are ordinarily used. However, the process of the invention makesit possible to apply to the gate busline a conductive layer formedaccording to a vacuum deposition method, a screen printing method, anink jet method or a plating method, all of which lower the layerproperties above but decrease cost.

[0090] Controlling the thickness of the insulation layer, parasiticcapacitance occurring at portions between the gate busline and a sourceelectrode, a drain electrode, a pixel electrode or a source busline canbe reduced, whereby retardation on drive of the TFT sheet can berestrained. In view of the above, the thickness of the insulation layeris from 0.5 to 10 μm, and preferably from 1 to 5 μm.

[0091] As a semiconductor material constituting a semiconductor layer,known ones such as a-Si (amorphous silicone), p-Si (poly-silicone) andan organic semiconductor material are used, and an organic semiconductormaterial is preferably used. As the organic semiconductive material,π-conjugate materials are used. Examples of the π-conjugate materialsinclude polypyrroles such as polypyrrole, poly(N-substituted pyrrole),poly(3-substituted pyrrole), and poly(3,4-disubstituted pyrrole);polythiophenes such as polythiophene, poly(3-substituted thiophene),poly(3,4-disubstituted thiophene), and polybenzothiophene;polyisothianaphthenes such as polyisothianaphthene;polythienylenevinylenes such as polythienylenevinylene;poly(p-phenylenevinylenes) such as poly(p-phenylenevinylene);polyanilines such as polyaniline, poly(N-substituted aniline),poly(3-substituted aniline), and poly(2,3-substituted aniline);polyacetylnenes such as polyacetylene; polydiacetylens such aspolydiacetylene; polyazulenes such as polyazulene; polypyrenes such aspolypyrene; polycarbazoles such as polycarbazole and poly(N-substitutedcarbazole), polyselenophenes such as polyselenophene; polyfurans such aspolyfuran and polybenzofuran; poly(p-phenylenes) such aspoly(p-phenylene); polyindoles such as polyindole; polypyridazines suchas polypyridazine; polyacenes such as naphthacene, pentacene, hexacene,heptacene, dibenzopentacene, tertabenzopentacene, pyrene, dibenzopyrene,chrysene, perylene, coronene, terylene, ovalene, quoterylene, andcircumanthracene; derivatives (such as triphenodioxazine,triphenodithiazine, hexacene-6,15-quinone) in which some of carbon atomsof polyacenes are substituted with atoms such as N, S, and O or with afunctional group such as a carbonyl group; polymers such as polyvinylcarbazoles, polyphenylene sulfide, and polyvinylene sulfide; andpolycyclic condensation products described in Japanese Patent O.P.I.Publication No. 11-195790.

[0092] Further, oligomers having repeating units in the same manner asin the above polymers, for example, thiophene hexamers includingα-sexithiophene, α, ω-dihexyl-α-sexithiophene,α,ω-dihexyl-α-quiinquethiophene, andα,ω-bis(3-butoxypropyl)-α-sexithiophene, or styrylbenzene derivatives,can be suitably employed.

[0093] Further, listed are metallophthalocyanines such as copperphthalocyanine, and fluorine-substituted copper phthalocyaninesdescribed in Japanese Patent O.P.I. Publication No. 11-251601;tetracarboxylic acid diimides of condensed ring compounds includingnaphthalene tetracarboxylic acid imides such as naphthalene1,4,5,8-teracarboxylic acid diimide,N,N′-bis(4-trifluoromethylbenzyl)naphthalene 1,4,5,8-tretracarboxylicacid diimide, N,N′-bis(1H,1H-perfluoroctyl)naphthalene1,4,5,8-tetracarboxylic acid diimide derivatives,N,N′-bis(1H,1H-perfluorobutyl)naphthalene 1,4,5,8-tetracarboxylic aciddiimide derivatives, N,N′-dioctylnaphthalene 1,4,5,8-tetracarboxylicacid diimide derivatives, and naphthalene 2,3,6,7-tetracarboxylic aciddiimides, and anthracene tetracarbocylic acid diimides such asanthracene 2,3,6,7-tetracarboxylic acid diimides; fullerenes such asC₆₀, C₇₀, C₇₆, C₇₈, and C₈₄; carbon nanotubes such as SWNT; and dyessuch as merocyanines and hemicyanines.

[0094] Of these π conjugate compounds, preferably employed is at leastone selected from the group consisting of oligomers which havethiophene, vinylene, thienylenevinylene, phenylenevinylene, p-phenylene,their substitution product or at least two kinds thereof as a repeatingunit and have a repeating unit number n of from 4 to 10, polymers whichhave the same unit as above and a repeating unit number n of at least20, condensed polycyclic aromatic compounds such as pentacene,fullerenes, condensed cyclic tetracarboxylic acid diimides of condensedring compounds, and metallo-phthalocyanines.

[0095] Further, employed as other materials for organic semiconductorsmay be organic molecular complexes such as a tetrathiafulvalene(TTF)-tetracyanoquinodimethane (TCNQ) complex, abisethylenetetrathiafulvalene (BEDTTTF)-perchloric acid complex, aBEDTTTF-iodine complex, and a TCNQ-iodine complex. Still further,employed may be σ conjugate polymers such as polysilane and polygermane,as well as organic-inorganic composite materials described in JapanesePatent O.P.I. Publication No. 2000-260999.

[0096] In the invention, the organic semiconductor layer may besubjected to a so-called doping treatment (referred to also as simplydoping) by incorporating in the layer, materials working as an acceptorwhich accepts electrons, for example, acrylic acid, acetamide, materialshaving a functional group such as a dimethylamino group, a cyano group,a carboxyl group and a nitro group, benzoquinone derivatives, ortetracyanoethylene, tetracyanoquinodimethane or their derivatives, ormaterials working as a donor which donates electrons, for example,materials having a functional group such as an amino group, a triphenylgroup, an alkyl group, a hydroxyl group, an alkoxy group, and a phenylgroup; substituted amines such as phenylenediamine; anthracene,benzoanthracene, substituted benzoanthracenes, pyrene, substitutedpyrene, carbazole and its derivatives, and tetrathiafulvalene and itsderivatives.

[0097] The doping herein means that an electron accepting molecule(acceptor) or an electron donating molecule (donor) is incorporated inthe organic semiconductor layer as a dopant. Accordingly, the layer,which has been subjected to doping, is one which comprises the condensedpolycyclic aromatic compounds and the dopant. As the dopant in thepresent invention, a known dopant can be used.

[0098] The methods for forming the organic semiconductor layer include avacuum deposition method, a molecular beam epitaxial growth method, anion cluster beam method, a low energy ion beam method, an ion platingmethod, a CVD method, a sputtering method, a plasma polymerizationmethod, an electrolytic polymerization method, a chemical polymerizationmethod, a spray coating method, a spin coating method, a blade coatingmethod, a dip coating method, a casting method, a roll coating method, abar coating method, a die coating method, an ink jet method and an LBmethod. These methods may be used according to kinds of materials used.However, of these, an ink jet method is preferred in view ofproductivity in which a thin layer with high precision can be easilyobtained employing a solution of an organic semiconductive material fromthe viewpoint of productive efficiency.

[0099] When a precursor such as pentacene is soluble in a solvent asdisclosed in Advanced Material 1999, Vol. 6, p. 480-483, a precursorlayer formed by coating of the precursor solution may be heat treated toform an intended organic material layer.

[0100] Another embodiment of the process of the invention formanufacturing the thin-film transistor sheet comprises, after the gateelectrode forming step, forming a semiconductor layer as a continuouslayer to cover each of the gate electrode of the plural thin-filmtransistors.

[0101] The TFT sheet of the invention can eliminate an influence of theelectric field effect of the gate busline, since the gate electrodecomprised of an electrode material, which has been allowed to permeatethe insulation layer, gives its electric field effect to thesemiconductor layer. That is, the TFT sheet employing the TFTs of theinvention makes it possible to drive each TFT in which each gateelectrode connected to the same gate busline is not substantiallyinfluenced by the electric field effect of the gate busline.Accordingly, a semiconductor layer in the specific form is notnecessary, and the semiconductor layer can be provided as continuouslayer to cover each gate electrode of the plural TFTs of the TFT sheet.This means that the TFT sheet can be manufactured simply and atextremely low cost, since the step of forming a semiconductor layer inthe specific form is eliminated during manufacture.

[0102] The thickness of the organic semiconductor layer is notspecifically limited. The thickness of the organic semiconductor layeris ordinarily not more than 1 μm, and preferably from 10 to 300 nm.

[0103] In the invention, materials for forming a source electrode, adrain electrode, a source busline, a gate busline and a pixel electrode,each of which is other than a gate electrode, are not specificallylimited, as long as they are electrically conductive. Examples thereofinclude platinum, gold, silver, nickel, chromium, copper, iron, tin,antimony, lead, tantalum, indium, palladium, tellurium, rhenium,iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tinoxide-antimony, indium oxide-tin (ITO), fluorine-doped zinc oxide, zinc,carbon, graphite, glassy carbon, silver paste as well as carbon paste,lithium, beryllium, sodium, magnesium, potassium, calcium, scandium,titanium, manganese, zirconium, gallium, niobium, sodium,sodium-potassium alloy, magnesium, lithium, aluminum, magnesium/coppermixtures, magnesium/silver mixtures, magnesium/aluminum mixtures,magnesium/indium mixtures, aluminum/aluminum oxide mixtures, andlithium/aluminum mixtures. Platinum, gold, silver, copper, indium,aluminum, indium oxide-tin (ITO) and carbon are preferred. Further,known electrically conductive polymers whose electrical conductivity isimproved by doping are preferably used. Examples thereof includeelectrically conductive polyaniline, electrically conductivepolypyrrole, electrically conductive polythiophene, and complex ofelectrically conductive polyethylenedioxythiophene and polystyrenesulfonic acid. Of these, ones, which provide a low electric resistanceat an interface with the semiconductor layer, are preferred.

[0104] As a method for forming the electrode, there are a method inwhich the electrode is formed according to a known photolithography orlift-off method from an electrically conductive layer of the conductivematerial described above formed according to a vacuum deposition methodor a sputtering method, a method in which the electrode is formedaccording to thermal transfer of the conductive material to a foil of ametal such as aluminum or copper, and a method in which the electrode isformed by etching a resist of the conductive material formed by an inkjet method. The electrode may be formed by ejecting in the form ofelectrode a solution or dispersion liquid of an electrically conductivepolymer or a dispersion liquid of electrically conductive particles ontothe surface on which the electrode is to be formed or by subjecting tophotolithography or laser ablation the coated layer of the solution orthe dispersion liquid. Further, employing ink or conductive pastecontaining an electrically conductive polymer or electrically conductiveparticles, the electrode may be forming by printing in the electrodepattern onto the surface on which the electrode is to be formedaccording to a printing method such as letterpress printing, intaglioprinting, planographic printing or screen printing.

[0105] Various insulating films may be employed as the gate insulatinglayer. The insulating layer is preferably an inorganic oxide filmcomprised of an inorganic oxide with high dielectric constant. Examplesof the inorganic oxide include silicon oxide, aluminum oxide, tantalumoxide, titanium oxide, tin oxide, vanadium oxide, barium strontiumtitanate, barium zirconate titanate, zirconic acid lead carbonate, leadlanthanum titanate, strontium titanate, barium titanate, bariummagnesium fluoride, bismuth titanate, strontium bismuth titanate,strontium bismuth tantalate, bismuth niobate tantalate, and yttriumtrioxide. Of these, silicon oxide, silicon nitride, aluminum oxide,tantalum oxide or titanium oxide is particularly preferred. An inorganicnitride such as silicon nitride or aluminum nitride can be also suitablyused.

[0106] The methods for forming the above film include a dry process suchas a vacuum deposition method, a molecular beam epitaxial growth method,an ion cluster beam method, a low energy ion beam method, an ion platingmethod, a CVD method, a sputtering method, or an atmospheric pressureplasma method, a wet process such as a spray coating method, a spincoating method, a blade coating method, a dip coating method, a castingmethod, a roll coating method, an bar coating method, or a die coatingmethod, and a patterning method such as a printing method or an ink-jetmethod. These methods can be used due to kinds of materials used in theinsulating layer.

[0107] As the typical wet process can be used a method of coating adispersion liquid and drying, the liquid being obtained by dispersinginorganic oxide particles in an organic solvent or water optionally inthe presence of a dispersant such as a surfactant, or a so-called solgel method of coating a solution of an oxide precursor such as analkoxide and drying.

[0108] Among the above, the preferred is an atmospheric pressure plasmamethod.

[0109] The insulating film formation method according to plasma atatmospheric pressure means a method wherein a reactive gas isplasma-excited by discharge conducted at atmospheric pressure or atapproximately atmospheric pressure, whereby a thin-film is formed on asubstrate. The method (hereinafter referred to also as an atmosphericpressure plasma method) is described in Japanese Patent O.P.I.Publication Nos. 11-61406, 11-133205, 2000-121804, 2000-147209, and2000-185362. This method can form a thin layer having high performanceat high productivity.

[0110] It is preferred that the gate insulating layer 3 is comprised ofan anodization film or an anodization film and an insulating film. Theanodization film is preferably subjected to sealing treatment. Theanodization film is formed on a metal capable of being anodized byanodizing the metal according to a known method.

[0111] Examples of the metal capable of being anodized include aluminumand tantalum. An anodization treatment method is mot specificallylimited and the known anodization treatment method can be used.Anodization treatment forms an oxidization film. An electrolyticsolution used in the anodization treatment may be any as long as it canform a porous oxidation film. Examples of electrolytes in theelectrolytic solution include sulfuric acid, phosphoric acid, oxalicacid, chromic acid, boric acid, sulfamic acid, benzene sulfonic acid ortheir salt, and a mixture thereof. Anodization treatment conditionscannot be specified since they vary due to kinds of an electrolyticsolution used. Generally, the concentration of the electrolytic solutionis from 1 to 80% by weight, temperature of the electrolytic solution isfrom 5 to 70° C., electric current density is from 0.5 to 60 A/dm²,voltage applied is from 1 to 100 V, and electrolytic time is from 10seconds to 5 minutes. It is preferred that an aqueous solution ofsulfuric acid, phosphoric acid or boric acid is used as an electrolyticsolution, and direct current is used. Alternating current can be alsoused. The concentration of the above acid of the electrolytic solutionis preferably from 5 to 45% by weight. Anodization treatment ispreferably carried out in the electrolytic solution at an electriccurrent density of from 0.5 to 20 A/dm² at a temperature of from 20 to50° C. for 20 to 250 seconds.

[0112] As the gate insulating layer, an organic compound film can bealso used. Examples of the organic compound used in the organic compoundfilm include polyimide, polyamide, polyester, polyacrylate, aphoto-curable resin such as a photo-radical polymerizable orphoto-cation polymerizable resin, a copolymer containing anacrylonitrile unit, polyvinyl phenol, polyvinyl alcohol, novolak resin,and cyanoethylpullulan.

[0113] As a method of forming the organic compound film, the wet processdescribed above is preferably used.

[0114] The inorganic oxide film and the organic oxide film can be usedin combination and superposed. The thickness of the insulating filmabove is generally 50 nm to 3 μm, and preferably from 100 nm to 1 μm.

[0115] An orientation layer may be provided between the gate insulatinglayer and the semiconductor channel. As the orientation layer, a selforganization layer is preferably used which is formed from a silanecoupling agent such as octadecyltrichlorosilane ortrichloromethylsilane, alkane phosphoric acid, alkane sulfonic acid, oran alkane carboxylic acid.

[0116] It is preferred that the process of the invention furthercomprises, between the step of the insulation layer providing step andthe fluid electrode material supplying step, the step of supplying aresin solution so that the resin is allowed to permeate portions otherthan portions of the insulation layer where the gate electrode is to beformed.

[0117] As the resin, the water soluble binders such as gelatin, a watersoluble polymer other than gelatin, latexes, and polyurethanes used inthe gate insulating layer above are used. The resin solution is obtainedby dissolving or dispersing the water soluble polymer in the solvent ordispersion medium used in the fluid electrode material solution ordispersion above.

[0118] The organic thin-film transistor (bottom gate type) of theinvention preferably comprises, between the substrate and the gateelectrode, a subbing layer containing a compound selected from inorganicoxides or inorganic nitrides or a subbing layer containing a polymer.

[0119] The inorganic oxides contained in the subbing layer includesilicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tinoxide, vanadium oxide, barium strontium titanate, barium zirconatetitanate, zirconic acid lead carbonate, lead lanthanum titanate,strontium titanate, barium titanate, barium magnesium fluoride, bismuthtitanate, strontium bismuth titanate, strontium bismuth tantalate,bismuth niobate tantalate, and yttrium trioxide. The inorganic nitridesinclude silicon nitride and aluminum nitride.

[0120] Of these, silicon oxide, aluminum oxide, tantalum oxide, titaniumoxide or silicon nitride is preferred.

[0121] In the invention, the subbing layer containing a compoundselected from inorganic oxides or inorganic nitrides is preferablyformed according to the atmospheric pressure plasma method describedabove, whereby a layer with high performance can be formed with highproductivity.

[0122] Examples of the polymer used in the subbing layer include apolyester resin, a polycarbonate resin, a cellulose resin, an acrylresin, a polyurethane resin, a polyethylene resin, a polypropyleneresin, a polystyrene resin, a phenoxy resin, a norbornene resin, anepoxy resin, vinyl chloride-vinyl acetate copolymer, a vinyl chlorideresin, vinyl acetate-vinyl alcohol copolymer, a partially saponificatedvinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidenechloride copolymer, vinyl chloride-acrylonitrile copolymer,ethylene-vinyl alcohol copolymer, polyvinyl alcohol, chlorinatedpolyvinyl chloride, ethylene-vinyl chloride copolymer, ethylene-vinylacetate copolymer, a polyamide resin, an ethylene-butadiene resin, abutadiene-acrylonitrile resin, a silicone resin, and afluorine-contained resin.

[0123] In the invention, the substrate 1 is a resin sheet comprised of aresin. Examples of the resin sheet include resin sheets comprised of,for example, polyethylene terephthalate (PET), polyethylene naphthalate(PEN), polyethersulfone (PES), polyetherimide, polyether ether ketone,polyphenylene sulfide, polyallylate, polyimide, polycarbonate (PC),cellulose triacetate (TAC), or cellulose acetate propionate (CAP) . Useof such a resin sheet makes it possible to decrease weight, to enhanceportability, and to enhance durability against impact due to itsflexibility, as compared to glass.

EXAMPLES

[0124] Next, the present invention will be explained employing examples,but is not limited thereto. In the examples, “parts” is part by weight,unless otherwise specified. In the following examples and comparativeexamples, a thin-film transistor sheet (TFT sheet) having the structureas shown in FIG. 7 was prepared. The TFT sheet as shown in FIG. 7 is anadditional capacitor type. In FIG. 7, the semiconductor layer 4 iscoated as a continuous layer on the entire surface on which thesemiconductor layer is to be formed. A drain electrode 5 and a sourceelectrode 6 are connected through the semiconductor layer 4, and furtherthrough a gate busline 12 and a source busline 13. Electrode 10 isformed in the insulation layer at the additional capacitor 20 in thesame way as the gate electrode 2 is formed according to the process ofthe invention. In FIG. 7, numerical number 9 is an output electrode.

Example 1

[0125] The silver paste available on the market was printed on a 200 μmthick PES film sheet according to a screen printing method to form agate busline with a thickness of 3 μm and with L/S=50 μm, which washardened by heating. Snowtex-PSM with a solid content of 20% by weight(produced by Nissan Kagaku Co., Ltd.) was coated on the gate busline toform and dried to form an insulation layer with a thickness of 3 μm.

[0126] An electrically conductive polymer solution, in which 0.05% byweight of a nonionic surfactant (polyoxyethylenealkyl ether) was addedto an aqueous dispersion (BAYTRON P produced by Bayer Co., Ltd.) of aPEDOT (polyethylenedioxythiophene)-PSS (polystyrene sulfonic acid)complex was ejected onto the insulation layer (at the portion as shownin FIG. 8) according to a piezo type ink jet head, where the solutionwas allowed to permeate the insulation layer and dried to form a gateelectrode. At this time, an electrode for additional capacitor may beformed.

[0127] Subsequently, the resulting material was subjected to atmosphericpressure plasma discharge treatment under the following conditions toobtain a 20 nm thick silicon oxide layer as a gate insulating layer.

[0128] (Gas Used) Inert gas: Helium 98.25% by volume Reactive gas: anoxygen gas  1.5% by volume Reactive gas: tetraethoxysilane vapor  0.25%by volume (bubbled in an argon gas) (Condition of discharge) Dischargeoutput power: 10 W/cm²

[0129] The resulting silicon oxide gate insulating layer was furthersubjected to atmospheric pressure plasma discharge treatment employingtrimethoxypropylsilane as a reactive gas to give a moisture repellentproperty.

[0130] Pentacene sublimation-purified was vacuum deposited onto theresulting gate insulation layer to form a semiconductor layer with athickness of 50 nm. At this time, the pentacene may be deposited eitherin the specific form through a mask or entirely on the surface of thegate insulating layer.

[0131] <Formation of Organic Semiconductor Layer Protective Layer>

[0132] An aqueous polyvinyl alcohol solution, in which purifiedpolyvinyl alcohol was dissolved in water sufficiently purified employinga super pure water manufacturing apparatus, was coated on the organicsemiconductor layer, and dried at 100° C. in a nitrogen atmosphere toobtain an organic semiconductor layer protective layer of polyvinylalcohol with a thickness of 1 μm.

[0133] <Formation of Light Sensitive Layer>

[0134] The following compositions A and B were individually kneaded, andthe kneaded composition A, B, and polyisocyanante compound describedabove were mixed in a ratio by weight of 100:2.39:0.37, and furtherstirred in a dissolver to obtain a coating solution.

[0135] The resulting coating solution was further ultrasonic dispersed,coated on the protective layer employing an extrusion coater, and driedat 100° C. for 5 minutes to obtain a light sensitive layer with athickness of 0.3 μm.

[0136] Composition A Composition A Fe-Al ferromagnetic metal powder  100 parts Polyrethane resin (Vylon UR-8200, produced  10.0 parts byToyobo Co., Ltd.) Polyester resin (Vylon 2800, produced  5.0 parts byToyobo Co., Ltd.) Phosphate  3.0 parts Methyl ethyl ketone 105.0 partsToluene 105.0 parts Cyclohexanone  90.0 parts Composition B α-Alumina(High purity alumina HIT60G,   100 parts average particles size: 0.18μm, produced by Sumitomo Kagaku Co., Ltd.) Polyrethane resin (VylonUR-8700, produced  15.0 parts by Toyobo Co., Ltd.) Phosphate  3.0 partsMethyl ethyl ketone  41.3 parts Toluene  41.3 parts Cyclohexanone  35.4parts

[0137] <Formation of Electrode Material-Repellent Layer>

[0138] A silicone rubber solution, in which the following composition 1was dissolved in Isopar E (isoparaffin type hydrocarbon, produced byExxon Co. Ltd.) to give a solid content of 10.3% by weight, was coatedon the light sensitive layer, and dried to form an electrodematerial-repellent layer with a thickness of 0.4 μm comprised ofsilicone rubber.

[0139] (Composition 1) α, ω-Divinylpolydimethylsiloxane 100 parts(Molecular weight 60,000) HMS-501(Methylhydrogensiloxane-dimethylsiloxane  7 parts copolymer havingmethyl groups on the chain ends, SiH number/molecular weight = 0.69mol/g, produced by Chisso Co., Ltd.)Vinyltris(methylethylketoxyimino)silane  3 parts SRX-212 (platinumcatalyst, produced by  5 parts Toray Dow Corning Silicone Co., Ltd.)

[0140] <Exposure and Development of Light Sensitive Layer>

[0141] The resulting material was exposed at an exposure energy densityof 300 mJ/cm² employing a semiconductor laser with an output power of100 mW emitting a 830 nm light form a source and drain (pixel) electrodepattern, and developed with a brush, whereby the silicone rubber layerat exposed portions was removed.

[0142] <Removal of Organic Semiconductor Layer Protective Layer>

[0143] The resulting material was further washed with water to removethe light sensitive layer and polyvinyl alcohol protective layer at theexposed portions.

[0144] <Formation of Source and Drain Electrodes, Source Busline andPixel Electrode>

[0145] An aqueous dispersion BAYTRON P (produced by Bayer Co., Ltd.) wascoated on the resulting material employing a roll coater, wherein thedispersion was adhered only to the portions at which the silicone rubberlayer at exposed portions was removed, and then dried at 100° C.

[0146] Further, a dispersion containing silver particles with an averageparticle size of 8 nm, prepared according to a method disclosed inJapanese Patent O.P.I. Publication No. 11-80647, was coated on theresulting material employing a roll coater, wherein the dispersion wasadhered only to the portions at which the silicone rubber layer atexposed portions was removed, and dried at 200° C. for 15 minutes toform a source electrode, a drain electrode, a source busline and a pixelelectrode. The resulting electrodes and source busline were comprised ofa 20 nm PEDOT-PSS complex layer and a 300 nm Ag particle layer. Thus,TFT sheet sample 1 was obtained.

[0147] The TFT sheet sample 1 obtained above exhibited good workingproperty as a p-channel enhancement type FET, and had a carrier mobilityat saturated region of 0.4 cm²/V·s.

Example 2

[0148] The TFT sheet sample 2 was prepared in the same manner as in theTFT sheet sample 1 above, except that aluminum was vacuum depositedthrough a mask on the PES film sheet to form a gate busline with athickness of 3 μm and with L/S=50 μm.

[0149] The TFT sheet sample 2 exhibited the same good results as the TFTsheet sample 1.

Example 3

[0150] The TFT sheet sample 3 was prepared in the same manner as in theTFT sheet sample 1 above, except that between the gate electrodeformation step and the gate insulating layer formation step, thefollowing composition 2 was coated on the insulation layer toincorporate into the insulation layer, dried at 90° C. for 5 minutes,and then hardened by being exposed for 4 seconds employing a 60 W/cmhigh pressure mercury lamp 10 cm distant from the layer.

[0151] (Composition 2) Dipentaerythritol hexacrylate monomer 60 gDipentaerythritol hexacrylate dimmer 20 g Dipentaerythritol hexacrylatetrimer 20 g or polymer higher than the trimer Diethoxybenzophenone  2 g(UV-initiator) Silicon-containing surfactant  1 g Methyl ethyl ketone 75g Methyl propylene glycol 75 g

[0152] The TFT sheet sample 3 exhibited the same good results as the TFTsheet sample 1.

[0153] The structure above increases a mechanical strength of theinsulation layer and adhesion between the gate insulating layer and theinsulation layer.

Example 4

[0154] The TFT sheet sample 4 was prepared in the same manner as in theTFT sheet sample 1 above, except that a chloroform solution of apurified regioregular poly(3-hexylthiophene) (produced by Ardrich Co.,Ltd.) was coated onto the silicon oxide layer in an nitrogen atmosphereemploying an applicator, dried at room temperature, and further heatedat 50° C. for 30 minutes in an nitrogen atmosphere to form apoly(3-hexylthiophene) semiconductor layer with a thickness of 50 nm,and a PVA semiconductor layer protective layer was not formed.

[0155] In the above, the dissolved oxygen in the regioregularpoly(3-hexylthiophene) chloroform solution was removed by bubbling withnitrogen.

[0156] The TFT sheet sample 4 exhibited good working property as ap-channel enhancement type FET, and had a carrier mobility at saturatedregion of 0.04 cm²/V·s.

Example 5

[0157] The TFT sheet sample 5 was prepared in the same manner as in theTFT sheet sample 1 above, except that an acetone solution ofcyanoethylpullulan (produced by Shietsu Kagaku Co., Ltd.) was coatedonto the insulation layer, and dried at 90° c to form a gate insulatinglayer with a thickness of 300 nm.

[0158] The TFT sheet sample 5 exhibited good working property as ap-channel enhancement type FET, and had a carrier mobility at saturatedregion of 0.3 cm²/V·s.

Comparative Example 1

[0159] The TFT sheet sample 6 (comparative) was prepared in the samemanner as in the TFT sheet sample 1 above, except that the insulationlayer was not provided.

[0160] When FET properties were measured, the TFT sheet sample 6 causedbreak-down between the gate busline and the source busline (dischargebreakdown of the insulation layer), and did not function as a thin-filmtransistor.

Comparative Example 2

[0161] The TFT sheet sample 7 (comparative) was prepared in the samemanner as in the TFT sheet sample 2 above, except that the insulationlayer was not provided.

[0162] When FET properties were measured, the TFT sheet sample 7 causedbreak-down between the gate busline and the source busline (dischargebreakdown of the insulation layer), and did not function as a thin-filmtransistor.

EFFECTS OF THE INVENTION

[0163] The present invention can minimize gate leakage caused byhillocks or edge portions of the electrode in a TFT, and can improvequality of a TFT sheet particularly when a resin sheet is used as asubstrate of the TFT sheet.

What is claimed is:
 1. A thin-film transistor comprising a substrate andprovided thereon, an insulation layer capable of receiving a fluidelectrode material, a gate electrode, a gate insulating layer, asemiconductor layer, a source electrode and a drain electrode, thesource electrode and the drain electrode connecting each other throughthe semiconductor layer, wherein the gate electrode is formed from thefluid electrode material which has been allowed to permeate theinsulation layer.
 2. The thin-film transistor of claim 1, wherein thesubstrate is comprised of a resin.
 3. The thin-film transistor of claim1, wherein the fluid electrode material is a solution of an electricallyconductive polymer or a dispersion liquid of an electrically conductivepolymer.
 4. The thin-film transistor of claim 1, wherein thesemiconductor layer is comprised of an organic semiconductor material.5. A process of manufacturing a thin-film transistor sheet, the processcomprising the steps of: providing a gate busline on a substrate;providing, on the surface of the substrate on the gate busline side, aninsulation layer capable of receiving a fluid electrode material;supplying the fluid electrode material to the insulation layer, thefluid electrode material being allowed to permeate the insulation layer;forming a gate electrode from the permeated fluid electrode material tobe in contact with the gate busline; forming a gate insulating layer onthe gate electrode; and forming a semiconductor layer on the gateinsulating layer.
 6. The process of claim 5, wherein the substrate iscomprised of a resin.
 7. The process of claim 5, wherein the fluidelectrode material is a solution of an electrically conductive polymeror a dispersion of an electrically conductive polymer.
 8. The process ofclaim 5, wherein the semiconductor layer is comprised of an organicsemiconductor material.
 9. The process of claim 5, between the step ofthe insulation layer providing step and the fluid electrode materialsupplying step, further comprising the step of supplying a resinsolution so that the resin is allowed to permeate portions other thanportions of the insulation layer where the gate electrode is to beformed.
 10. The process of claim 5, wherein the semiconductor layer isformed as a continuous layer over the entire surface on which thesemiconductor layer is to be formed.
 11. A thin-film transister sheetmanufactured according to the process of claim 5.